The long-range goal of the Program is to gain a thorough understanding of the complex sensory and neural bases of hearing and hearing impairment. The present proposal addresses complementary sets of questions related to a major theme of the Program: neural processing of the natural and spatial location of complex sound. It represents an integrated series of studies featuring novel experimental approaches conduced by a multi-disciplinary team of established investigators who, collectively, bring to the Program a record of productive interaction and expertise in a wide variety of disciplines including neurophysiology, membrane biophysics, neuroanatomy, electronic and computer engineering, statistical analysis, mathematical modeling, physical acoustics, signal processing, and human and animal behavior and psychoacoustics. Experiments are proposed that span cellular, system and behavioral levels. Specifically, the collaborative efforts includes studies of 1) processing speech and complex sounds by the cochlear nuclei, including structure/function studies at the cellular level and complementary animal psychophysics, 2) brainstem mechanisms involved in spatial localization, with special emphases on the precedence effect, the physiology and connectivity of auditory brainstem nuclei, and the coding of auditory spatial cues, 3) auditory cortical mechanisms of spatial hearing, with emphases on encoding sound motion and directional signals in background noise 4) structure/function relationships underlying auditory cortical processing, dealing with intrinsic and synaptic mechanisms and neural circuitry in auditory cortex and 5) human sound localization with emphases on processing of monaural directional cues and cues involved in moving sounds sources. The Program promotes interaction between and among investigators through such means as collaboration on research projects, sharing of core facilities and technical support staff, sharing of computer programs and databases over a network, and participation in regulated and frequent seminars that emphasize informal sharing of ideas and critical evaluation of research in progress. This work constitutes a series of necessary steps in understanding fundamental structure and function of the normal auditory system, which is essential to understanding mechanisms that underlie hearing impairment and to devising new strategies for diagnosis, intervention and treatment of disorders of hearing, speech and language.